Many combine harvesters employ the use of a conveyor to carry crop from the header into the threshing system of the machine. Typically the conveyor is comprised of an idler and a shaft assembly, having a looped chain passing around each assembly engaged by a sprocket. Typically, the conveyor is powered via a drive gear affixed to one of the shaft assemblies, thereby driving the looped chain. In most instances, each shaft assembly has a plurality of sprockets and a plurality of chains. In some systems, crop grabbing members are affixed to the chains such that as the sprocket and shaft assembly turns, the chain and grabbing members are moved as a result. The crop material is thus conveyed from the ground to the threshing (or other) system of the machine. The sprocket and shaft assemblies may be an assembly of lose components or a single piece welded assembly.
Due to the nature of the operating environment, this conveyor system needs to be protected from excessive loading caused by foreign objects. On occasion, a rock or other foreign object can cause the conveyor to partially or completely jam. In these instances, the gear can continue to drive the assembly creating unwanted forces in the shaft assembly and consequently in the chains. Damage to the gear, driver motor, shaft assembly and/or chain(s) can result. Aside from the cost of maintenance, such damage also results in down time and loss of crop harvest, which is undesirable.
Some currently available combines offer an optional mechanical rock detection system in which a high speed beater is used to discharge rocks and other foreign objects from the crop material as it is conveyed into the machine. In many combines, each of the conveyor and the beater is driven separately. Thus, the conveyor and its driver as well as the beater and its driver are handled separately, and each could be subject to jamming, although it is more common in the conveyor section.
In some combines, such as the flagship Axial Flow combines manufactured by CaseIH, the rock trap configuration includes a single gearbox that supplies power to both the conveyor drive shaft and rock trap beater. Due to packaging and driveline constraints, the configuration of this gearbox is such that the conveyor drive shaft and beater are mechanically connected to one another through the internal gear set, and a torque limiting device, in this case a wet fiction disk clutch, which is located between this gear set and the gear box input. As a result of this gearbox configuration, the inertia generated by these two rotating devices is connected as well. Therefore in the event that the conveyor is stopped suddenly by a foreign object, the inertia of the heavy, high speed beater must be stopped as well, or those forces will be applied to the conveyor and its drive system. As described above, such forces can cause damage to the conveyor drive system, the shaft assembly or the chains.
A conveyor assembly, driveline, and support structure design capable of stopping this inertial load would be excessively heavy and costly. Accordingly, another solution is needed.
Accordingly, better ways of absorbing, controlling, limiting, stopping, or preventing excess forces from developing in the conveyor system or its driveline, are needed. Specifically, a way of isolating the conveyor system, in single gear box setups, from the heavy rock trap beater is needed. The invention disclosed herein is useful for each of these situations and is a marked improvement which should result in less damage and downtime.